In the prior art, there are a large number of intervertebral linking devices. This type of device traditionally comprises bone anchoring elements, such as pedicular implantation screws or single or double vertebral hooks each equipped with a fixing head for a linking rod interconnecting said implants. The bone anchoring elements are distributed along the zone of the rachis to be treated to allow the mounting of two linking rods extending approximately parallel to each other by being placed on each side of the processi spinosus of the vertebrae. Sometimes a transversal crossing over between the linking rods is used to render the embodied construction more stable.
One of the difficulties for placing this intervertebral linking device concerns the connection between the intervetrebral linking rods and the bone anchoring elements. This connection is rendered delicate owing in particular to the non-alignment inside the frontal plane of the bone anchoring elements of the difference in height between the bone anchoring elements and the angulation imposed by the anatomy of the rachis to be treated. These connection difficulties of these linking rods frequently reveal mechanical stresses which need to be added to those generated by an applied corrective or stabilizing action and which are likely to result in the pulling up, at least partially, of the bone anchoring elements, indeed a fracture of one of the main portions of this intervertebral linking device.
So as to try to overcome these drawbacks, the patent U.S. Pat. No. 5,437,671 describes an intervertebral linking device comprising a transversal connection bar secured to bone anchoring elements and equipped with two fixing systems for linking rods. Each fixing system of a linking rod is mounted on the connection bar by means of two hooks.
It is to be noted that this fixing system does not comprise any means to ensure it is locked in a fixed specific position along this connection bar. Furthermore, this document does not describe the mounting of the connection bar with a possibility of rotation around its axis and locking in a specific fixed position with respect to the anchoring screws.
Thus, this intervertebral linking device does not allow the linking rod to be adapted on the connection bar according to the three planes of the space. Moreover, this device does not make it possible to obtain a rigid structure between the linking rods and the transversal connection bars.
An examination of previous known solutions shows that there is a need to have available an intervertebral linking device designed in such a way with respect to the angular shift imposed by the rachis so as to facilitate the connection between the bone anchoring elements and an intervertebral linking rod whilst limiting the mechanical stresses imposed on the various main portions of such a linking device, especially by eliminating the stresses generated by the simple linking of the various anchoring elements whose alignment along the three planes of space can be faulty.